Many railway operations require knowledge of the position and direction of railway vehicles. Routing of railway vehicles from one destination to another requires knowledge of the position of the railway vehicles in order to develop the optimal routing system.
Often times knowledge of the accurate position of a specific railway vehicle is necessary to execute railway operations. For instance, wheel detection devices can be utilized to identify when the railway vehicle is at the correct distance such that a car retarder mechanism can be applied.
Also, it is desirable to know when the railway vehicle is in the exact position or spot where coal is to be dumped from the vehicle into a collection bin in order that no coal is spilled during the transfer from the vehicle to the bin. Only when the vehicle is known so be in the correct position should the transfer operation be initiated.
Further, bar code readers can be utilized to identify the specific railway vehicle upon which the dumping operation is done. The sensing of a railway vehicle by a detection device triggers the bar code reader positioned along the track to receive the signal of the specific railway vehicle. Then, when the detection device senses the vehicle is out of the bar code reader zone, the bar code reader may be turned off. By activating the bar code reader system when a railway vehicle is in its reading zone and deactivating the reader when there are no railway vehicles in the zone, energy can be saved.
The prior art has developed detection devices which utilize a receiver and transmitter coil configuration for sensing the presence and direction of a railway vehicle. Some of these detecting devices are subject to inaccuracies where there is an increase in temperature or where there is interference from debris located near the coils. Both of these conditions can create drift which make sensing the position and direction of the railway vehicle difficult.
Most prior art devices generally do not provide a railway detection device able to be used in the presence of the large traction propulsion current of an electrified railroad. This is because the large currents may saturate the receiver amplifier and/or coils such that it is difficult to sense the presence of the railway vehicle wheel.
Flange detectors are also used in the prior art to detect the presence of a railway vehicle. In some of these cases, she detection devices consist of a magnet and a Hall effect sensor which sense a magnetic field in the flange of a railway wheel. As in the conventional transmitter/receiver coil wheel detectors, flange detectors may not accurately detect the presence of a railway vehicle in the presence of debris or high ambient temperature. Further, a flange may break from the rest of the wheel or deteriorate due to wear. In this situation, the detection device may not sense the railway vehicle.